JP2022167130A - Inkjet ink, tablet, printer, and tablet production method - Google Patents

Abstract

To provide: an inkjet ink which can protect a printed image and improve the discharge stability of a water-soluble pre-printing ink; a tablet having a printed part printed with the inkjet ink; a printer capable of printing the inkjet ink; and a production method of the tablet.SOLUTION: The inkjet ink according to an embodiment is an overcoat ink containing a coating material soluble both in water and in alcohol.SELECTED DRAWING: None

Description

The present invention relates to inkjet inks, tablets, printing presses and methods of making tablets.

Inks for inkjet printing (hereinafter also simply referred to as “inkjet inks”) include edible inks (edible inkjet inks). When solid formulations such as tablets and capsules are used as printed materials, edible inkjet inks include, for example, water-soluble inks using water-soluble food dyes as coloring materials (for example, Patent Document 1).
Conventionally, for the purpose of protecting printed images formed with water-soluble inks, there has been a technique of providing an overcoat layer by printing an overcoat inkjet ink (hereinafter also simply referred to as "overcoat ink") on a printed image. known (for example, Patent Documents 2 and 3). Here, the protection of the printed image means preventing the transfer of the printed image by improving the dryness, abrasion resistance, etc. of the printed image, for example.

For example, in Cited Document 3, a coating liquid (overcoat ink) containing a water-insoluble material (for example, shellac resin) is used to improve the abrasion resistance of the printed image and prevent bleeding and transfer of the printed image. Techniques for forming a coat layer have been disclosed.

Japanese Patent Application Laid-Open No. 2006-169301 International Publication No. 2018/168733 Japanese Unexamined Patent Application Publication No. 2020-19906

The overcoat layer is formed by printing an overcoat ink on the printed image after forming a printed image with preprinted ink (for example, water-soluble ink) for forming the printed image. Overcoat ink ejected from an inkjet head in a printing machine may adhere to an inkjet head that ejects preprinted ink. Here, when the preprinting ink is a water-soluble ink, if a coating liquid made of a water-insoluble material is used as the overcoat ink, the overcoat ink adhering to the ink-jet head for the preprinting ink becomes water-soluble preprinting ink. Solidification without dissolution and precipitation of the coating agent may occur. As a result, the inkjet head for the preprinted ink may be clogged and the ejection stability of the preprinted ink may deteriorate. In other words, there is a risk that the ejection stability of the inkjet ink will be lowered in the printing machine.
Also, if a coating liquid made of a material that is insoluble in an organic solvent (such as alcohol) is used as the overcoat ink, the overcoat ink that adheres to the inkjet head of the preprinted ink may Solidification and deposition of the coating agent may occur without dissolving in the water-soluble preprinting ink. Further, the coating liquid becomes an overcoat ink containing water as a main solvent in order to dissolve the coating agent. For this reason, even if the overcoat ink is printed on top of the preprinted ink, the overcoat ink does not adhere to the printed image, and the drying property deteriorates, which may reduce the protective effect of the printed image.

The present invention has been made in view of such points, and an inkjet ink capable of protecting a printed image and improving the ejection stability of a water-soluble preprinting ink, and a printing portion printed with the inkjet ink. , a printer capable of printing the inkjet ink, and a method for manufacturing the tablet.

To achieve the above object, an inkjet ink according to one aspect of the present invention is characterized by being an overcoat ink containing a coating agent that dissolves in both water and alcohol.

Moreover, in order to achieve the above object, a tablet according to one aspect of the present invention is characterized by including a printed portion printed using the inkjet ink.

Further, in order to achieve the above object, a printing machine according to one aspect of the present invention is a printing machine capable of printing on a printing substrate with at least two types of inkjet inks, contains at least a first inkjet ink, which is the above inkjet ink, and a second inkjet ink containing water as a main solvent and at least one coloring material, and the second inkjet ink is applied to the printing substrate. It is characterized in that it is possible to print the first inkjet ink overlaid after printing the ink.

In order to achieve the above object, a method for producing a tablet according to one aspect of the present invention includes a printing step of printing a first inkjet ink, which is an overcoat ink containing a coating agent that dissolves in both water and alcohol. characterized by including at least

According to one aspect of the present invention, it is possible to protect the printed image and improve the ejection stability of the preprinted ink used for forming the printed image.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows typically the structural example of the printing press which concerns on embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing which shows an example of the tablet (uncoated tablet) which concerns on embodiment of this invention. 1 is a schematic cross-sectional view showing an example of a tablet (film-coated tablet) according to an embodiment of the present invention; FIG. 1 is a plan view showing a configuration example of a tablet (uncoated tablet) according to an embodiment of the present invention; FIG. 1 is a plan view showing a configuration example of a tablet (film-coated tablet) according to an embodiment of the present invention. FIG.

The inkjet ink according to the embodiment of the present invention is, for example, an overcoat ink (first (an example of inkjet ink). Hereinafter, an overcoat ink according to an embodiment of the present invention, a tablet provided with a printed portion printed with the overcoat ink, a configuration of a printing machine for printing the inkjet ink, and a method for manufacturing the tablet will be described in detail.

[Ink set]
In this embodiment, an ink set containing at least a combination of a water-soluble ink and an overcoat ink is used. This ink set is used in an inkjet printer (an example of a printing machine) that prints on a substrate (eg, solid formulation) by an inkjet method. A printed image is formed with a water-soluble ink on a printing substrate (eg, solid formulation) to be printed. In this embodiment, an overcoat layer is formed by further printing overcoat ink on the printed image. As a result, the printed image can be protected to prevent transfer or the like, and the printed image can be fixed to the substrate.

As described above, both the overcoat ink and the water-soluble ink (an example of the second inkjet ink) according to the present embodiment are inkjet inks, that is, ink compositions used in inkjet printers. Moreover, both the overcoat ink and the water-soluble ink according to the present embodiment are edible. The edibility of the overcoat ink and the water-soluble ink is imparted by using, for example, materials conforming to the standards of pharmaceutical additives stipulated by the Pharmaceutical Affairs Law, the Japanese Pharmacopoeia, or the Official Code of Food Additives.

[Structure of water-soluble ink]
The composition of the water-soluble ink for forming a printed image on the printing substrate will be described below.
In this embodiment, the water-soluble ink is a water-soluble inkjet ink containing water as a main solvent and at least one coloring material. Here, the water-soluble ink refers to an inkjet ink in which a coloring material is dissolved or dispersed in water, which is the main solvent, and stabilized.
The colorant contained in the water-soluble ink is not particularly limited as long as it is edible. Colorants that can be added to the inkjet ink according to the present embodiment can be added by appropriately selecting, for example, conventionally known synthetic food colors and natural food colors.

Synthetic food colorings include, for example, tar colorings, natural coloring matter derivatives, natural synthetic coloring matter, and the like. Examples of tar pigments include Food Red No. 2 (Amaranth, FDA Name: FD & C Red No. 2, Color Index Name: Acid Red 27, CAS Number: 915-67-3), Food Red No. 40 (Allura Red AC, FDA Name: FD & C Red No. 40, Color Index Name: Food Red 40, CAS Number: 25956-17-6), Edible Red No. 102 (New Coccine, Color Index Name: Acid Red Number 18, CAS Food Red No. 104 (Phloxine, FDA Name: D&C Red No. 28, Color Index Name: Acid Red 92, CAS Number: 18472-87-2), Food Red No. 105 (Rose bengal, Color Index Name: Acid Red 94, CAS Number: 632-69-9), Food Red No. 106 (Acid Red, Color Index Name: Acid Red 52, CAS Number: 3520-42-1), Food Yellow No. 4 (Tartrazine , FDA Name: FD & C Yellow No. 5, Color Index Name: Acid Yellow 23, CAS Number: 1934-21-0), Edible Yellow No. 5 (Sunset Yellow FCF, FDA Name: FD & C Yellow No. 6, Color Index Name: Food Yellow 3, CAS Number: 2783-94-0), Food Blue No. 1 (Brilliant Blue FCF, FDA Name: FD & C Blue No. 1, Color Index Name: Food Blue N84, CAS 4) -45-9), Food Blue No. 2 (Indigo Carmine, FDA Name: FD & C Blue No. 2, Color Index Name: Acid Blue 74, CAS Number: 860-22-0), Food Red No. 2 Aluminum Lake ( FD&C Red No. 2 Aluminum Lake), Food Red No. 3 Aluminum Lake (FD & C Red No. 3 Aluminum Lake), Food Red No. 40 Aluminum Lake (FD & C Red No. 40 Aluminum Lake), Food Yellow No. 4 Aluminum Lake (FD & C Red No. 40 Aluminum Lake) C Yellow No. 5 Aluminum Lake), Edible No. 5 Aluminum Lake (FD & C Yellow No. 6 Aluminum Lake), Edible Blue No. 1 Aluminum Lake (FD & C Blue No. 1 Aluminum Lake), Edible Blue No. 2 Aluminum Lake (FD & C Blue No. 2 Aluminum Lake) and the like.
Examples of natural pigment derivatives include norbixin potassium and the like. Examples of natural synthetic pigments include β-carotene, riboflavin and the like.

The above-mentioned "Color Index Name" is established by the American Association of Textile Chemists and Colorists. Moreover, the above-mentioned "FDA Name" is established by the US FDA (Food and Drug Administration, US Food and Drug Administration). In this embodiment, each dye (each substance) that can be used is specified using the CAS Number, but the present invention is not limited to this. For example, although the substance name is the same as the dye (substance) described in this embodiment, it is a geometric isomer, a stereoisomer, a substance containing an isotope element, or a salt thereof, so that a different CAS number is given. The pigments (substances) used in the present invention can of course also be used in this embodiment. In addition, when there is no isomer or the like, or when usable dyes (substances) are specified (limited), the substance (compound) itself of the CAS Number described in this embodiment can be used.

Examples of natural edible dyes include anthocyanin dyes, carotenoid dyes, quinone dyes, chlorophyll dyes, flavonoid dyes, betaine dyes, monascus dyes, and other dyes derived from natural products. Examples of anthocyanin pigments include red radish pigment, red cabbage pigment, red rice pigment, elderberry pigment, cowberry pigment, gooseberry pigment, cranberry pigment, salmonberry pigment, perilla pigment, swim blueberry pigment, strawberry pigment, and dark sweet. cherry pigment, cherry pigment, hibiscus pigment, huckleberry pigment, grape juice pigment, grape skin pigment, black currant pigment, blackberry pigment, blueberry pigment, plum pigment, whiteberry pigment, boysenberry pigment, mulberry pigment, purple sweet potato pigment , purple corn pigment, purple yam pigment, raspberry pigment, red currant pigment, loganberry pigment, and other anthocyanin pigments. Examples of carotenoid pigments include annatto pigments, gardenia yellow pigments, and other carotenoid pigments. Examples of quinone-based dyes include cochineal dyes, chikon dyes, lac dyes, and other quinone-based dyes. Examples of flavonoid pigments include safflower yellow pigment, sorghum pigment, onion pigment, and other flavonoid pigments. Examples of betaine dyes include beet red dyes. Monascus dyes include, for example, monascus dyes and monascus yellow dyes. Other pigments originating from natural products include, for example, turmeric pigments, rabbit pigments, gardenia red pigments, and spirulina blue pigments.

(carbon)
Further, in the present embodiment, the water-soluble ink may contain carbon.
Carbon contained in the water-soluble ink is not particularly limited. is. Among these carbons, those that can be orally ingested are particularly preferable. When orally ingestible carbon is used, the inkjet ink according to the present embodiment can be used for direct printing on tablet surfaces, direct printing on food, and packaging for direct contact with pharmaceuticals and food.

(solvent)
In this embodiment, the water-soluble ink contains a solvent for dispersing the aforementioned coloring material (food dye or carbon). A water-soluble ink contains water as a main solvent and an alcohol solvent as a drying solvent. The main solvent and dry solvent are described below.
The main solvent contained in the inkjet ink according to this embodiment is water, for example, purified water. In addition, the above-mentioned "main solvent" means the component with the largest mass ratio in the whole solvent. In this embodiment, the proportion of water as the main solvent contained in the water-soluble ink is, for example, 50 mass % or more of the entire inkjet ink.

In this embodiment, the dry solvent contained in the water-soluble ink is an alcohol solvent. As the alcohol solvent, for example, an alcohol solvent containing at least one of ethanol, isopropyl alcohol (IPA) and normal propyl alcohol (NPA) can be used. The concentration of the alcohol solvent may be 35 parts by mass or less with respect to the entire inkjet ink. If the concentration of the alcohol solvent exceeds 35 parts by mass relative to the entire inkjet ink, the ink tends to dry excessively and the intermittent resumability tends to deteriorate. Also, the lower limit of the concentration of the alcohol solvent is not particularly limited, but is, for example, 0.001 parts by mass or more with respect to the entire inkjet ink. Within the above numerical range, it is possible to reduce the decrease in intermittent restartability.

(dispersant)
In this embodiment, the water-soluble ink may contain a dispersant in addition to the coloring material (food dye, carbon) and solvent described above. For example, when the water-soluble ink contains carbon as a coloring material, it preferably contains a dispersant that enhances the dispersibility of carbon. The dispersant may be one that can enhance the dispersibility of carbon and has edibility. As the dispersant, for example, a sucrose fatty acid ester having an HLB value within the range of 11 or more and 20 or less can be used. The content of the sucrose fatty acid ester may be within the range of 48% by mass or more and 100% by mass or less with respect to the above carbon. If the content of the sucrose fatty acid ester, which is a dispersant, is less than 48% by mass relative to the carbon, the dispersion stability of the carbon tends to decrease. Moreover, when the content of the sucrose fatty acid ester as a dispersant exceeds 100% by mass with respect to the above-mentioned carbon, there is a tendency that the drying property is lowered.

(wetting agent)
In the present embodiment, the water-soluble ink may contain a wetting agent in addition to the coloring material, solvent, and dispersant described above, and the content thereof is 0.001 parts by mass or more relative to the total mass of the inkjet ink. It may be in the range of 40 parts by mass or less. With such a configuration, drying of the water-soluble ink at the nozzles (inkjet nozzles) of the inkjet head can be prevented, and sufficient intermittent resumability can be imparted to the ink. If the content of the humectant is less than 0.001 part by mass relative to the total amount of the inkjet ink, the water-soluble ink tends to be dried and the resumability of printing tends to deteriorate. Moreover, if the content of the humectant exceeds 40 parts by mass with respect to the total mass of the water-soluble ink, the drying property of the ink may be reduced. As a result, the overcoat ink printed on the printed image may become wet, reducing the protective effect of the printed image.

Specific examples of the wetting agent according to this embodiment include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, pentamethylene glycol, trimethylene glycol, 2-butene-1, 4-diol, and 2-ethyl-1. , 3-hexanediol, 2-methyl-2,4-pentanediol, tripropylene glycol, polyethylene glycol having a number average molecular weight of 2000 or less, 1,3-propylene glycol, isopropylene glycol, isobutylene glycol, glycerin, mesoerythritol, penta Erythritol, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone and the like. Among these humectants, humectants containing at least one of propylene glycol and glycerin are particularly preferred. With such a configuration, in the present embodiment, it is possible to impart sufficient drying properties to the water-soluble ink, and further reduce deterioration in resumability of printing.
Moreover, the wetting agent according to the present embodiment may be used, for example, singly or in combination of two or more.

(binder)
In this embodiment, the water-soluble ink may contain a binder in addition to the above-described colorant (food dye, carbon), solvent, dispersant, and wetting agent. In the present embodiment, the binder that can be added to the water-soluble ink is not particularly limited as long as it is generally added to inkjet ink as a binder, and includes, for example, polysaccharides. Moreover, the polysaccharide contained in the binder according to the present embodiment preferably has a weight-average molecular weight within the range of 1,000 or more and 10,000 or less. With such a configuration, it is possible to impart sufficient drying properties to the water-soluble ink, and to further reduce deterioration in resumability of printing. If the weight-average molecular weight of the polysaccharide used as the binder is less than 1,000, it tends to be difficult to impart sufficient drying properties to the water-soluble ink. Further, when the weight average molecular weight of the polysaccharide used as the binder exceeds 10,000, the resumability of printing tends to deteriorate.

Also, the content of the binder according to this embodiment is preferably 0.01% by mass or more and 10% by mass or less of the total mass of the water-soluble ink. When the content of the binder is within the above range, the viscosity of the ink is such that ink-jet printing can be suitably performed.
Examples of binders according to the present embodiment include maltodextrin, erythritol, PVP (polyvinylpyrrolidone), dextran, polydextrose, starch substances such as corn and wheat, cellulosic substances such as carboxymethylcellulose and hydroxymethylcellulose, sodium alginate, Polysaccharides such as gum arabic, locust bean gum, tranto gum, guar gum, and tamarind seed.

(leveling agent)
In this embodiment, the water-soluble ink may contain a leveling agent in addition to the dye, solvent, or binder described above. In this embodiment, the leveling agent that can be added to the water-soluble ink may be an edible and water-soluble surfactant. Examples of the leveling agent include polyglycerin fatty acid esters (eg, Taiyo Kagaku Co., Ltd. decaglycerin distearate Q-182S, Taiyo Kagaku Co., Ltd. decaglycerin monolaurate Q-12S), sorbitan fatty acid esters (eg, Nikko Chemicals Co., Ltd. NIKKOLSL-10). ), sucrose fatty acid ester (eg, DK Ester F-110 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), polysorbate (Emsol S-120 series manufactured by Kao Corporation), and the like.

[Structure of overcoat ink]
Next, the composition of the overcoat ink for forming an overcoat layer on the printed image on the printing substrate (eg, solid formulation) will be described.
The overcoat ink according to this embodiment contains a coating agent that dissolves in both water and alcohol. The coating agent improves the drying property of the printed image when the overcoat layer is formed with the overcoat ink. As a result, the printed image formed with the water-soluble ink is prevented from being transferred, and the printed image can be protected.

Moreover, the overcoat ink according to the present embodiment can improve the ejection stability of the water-soluble ink by including a coating agent that dissolves in both water and alcohol.
The water-soluble ink may contain an alcohol solvent as a drying solvent as described above. Since the overcoat ink according to the present embodiment has a structure in which the coating agent dissolves in both water and alcohol, it also dissolves in water-soluble inks containing alcohol solvents. Therefore, for example, when the overcoat layer is formed, the overcoat ink adhered to the inkjet head that ejects the water-soluble ink dissolves in the water-soluble ink. Therefore, it is possible to suppress the solidification of the overcoat ink adhering to the inkjet head, and it is possible to improve the ejection stability of the water-soluble ink, such as the resumability of printing (intermittent resumability) and continuous printing. The intermittent resumability indicates the ejection stability when the inkjet ink held in the inkjet head for a long time is ejected, and the continuous printability indicates the ejection stability when the inkjet ink is continuously ejected from the inkjet head.
As described above, the overcoat ink according to the present embodiment can both protect the printed image and improve the ejection stability of the water-soluble ink.

(coating agent)
The overcoat ink according to this embodiment contains a coating agent as a binder. As described above, the coating agent contained in the overcoat ink according to the present embodiment has the property of being “soluble in both water and alcohol”. Specifically, the coating agent used in the overcoat ink according to the present embodiment has a solubility of 1% by mass or more in ethanol at 25°C, a solubility of 1% by mass or more in isopropyl alcohol at 25°C, and a solubility of 1% by mass or more in isopropyl alcohol at 25°C. is preferably 1% by mass or more in normal propyl alcohol.
Although details will be described later, these alcohols (ethanol, isopropyl alcohol and normal propyl alcohol) are used as solvents for the overcoat ink according to the present embodiment. Therefore, in the present embodiment, the coating agent is configured to satisfy the above-described solubility conditions in the above-described alcohols, so that the coating agent remains undissolved (insoluble matter) during the production of the overcoat ink. It is possible to suppress the generation and ensure the solubility of the coating agent. Further, the solubility of the coating agent in the above-mentioned alcohols should be 25% or less. As a result, it is possible to more reliably suppress the generation of undissolved coating agent (insoluble matters).

Further, the coating agent in the overcoat ink is a mixed solvent in which the mass ratio of alcohol solvent (at least one of ethanol, isopropyl alcohol and normal propyl alcohol) and water at 25° C. (alcohol solvent:water) is 1:1. is preferably 0.5% by mass or more. As a result, when the coating agent is added to the mixed solvent of alcohol solvent and water, undissolved matter (insoluble matter) does not occur, and the undissolved coating agent does not occur when manufacturing the overcoat ink using the mixed solvent. It can be suppressed to ensure the solubility of the coating agent. Moreover, the solubility of the coating agent in the above mixed solvent should be 25% or less.

Water, ethanol, isopropyl alcohol, and normal propyl alcohol are materials used as solvents in water-soluble inks, as described above. In other words, in the present embodiment, the overcoat ink is a water-soluble ink solvent because the coating agent satisfies the above-described solubility conditions in alcohol or a mixed solvent of water and alcohol. dissolves in Therefore, when the overcoat ink scatters, the coagulation of the overcoat ink and the undissolved coating agent (precipitation) in the inkjet head that ejects the water-soluble ink are suppressed, and the ejection stability of the water-soluble ink is further improved. can do.

Coating agents contained in the overcoat ink according to the present embodiment include methacrylic acid copolymer L, methacrylic acid copolymer LD, methacrylic acid copolymer S, aminoalkyl methacrylate copolymer E, ammonioalkyl methacrylate copolymer, hydroxypropyl cellulose, and ethyl cellulose. and polyvinyl acetal diethylaminoacetate.
These coating agents satisfy the solubility conditions in water and alcohol solvents (ethanol, isopropyl alcohol, and normal propyl alcohol), and can improve the ejection stability of water-soluble inks.
At least one of these may be used as the coating agent in the overcoat ink according to the present embodiment, or two or more may be mixed and used.

At least one of methacrylic acid copolymer L and ammonioalkyl methacrylate copolymer is preferably used as the coating agent in the overcoat ink according to the present embodiment. Further, from the viewpoint of protecting printed images formed with water-soluble ink, it is more preferable to use an ammonioalkyl methacrylate copolymer having excellent drying properties. As a result, the drying property of the printed image is further improved, and the transfer of the printed image can be prevented more reliably.

Moreover, the content of the coating agent described above is preferably in the range of 1% by mass or more and 25% by mass or less with respect to the entire overcoat ink according to the present embodiment.
By setting the content of the coating agent within the range of 1% by mass or more and 25% by mass or less, it is possible to protect the printed image by improving the drying property of the printed image and to improve the ejection stability of the overcoat ink and the water-soluble ink. can be more reliably compatible.
Here, from the viewpoint of improving ejection stability, the content of the coating agent is preferably 10% or less, more preferably 2.5% by mass or less. By setting the content of the coating agent to 10% or less, deposition of the coating agent due to drying of the overcoat ink can be suppressed, and ejection stability such as intermittent restartability and continuous printability can be further improved. Further, by setting the content of the coating agent to 2.5% by mass or less, the ejection stability can be further improved.
Moreover, from the viewpoint of reducing the amount of overcoat ink used during printing, it is preferable that the content of the coating agent exceeds 10% by mass. In this case, the printability (ejection stability) tends to be slightly lower than when the content of the coating agent is 10% by mass or less, but the amount of overcoat ink used during printing can be suppressed to a small amount. Therefore, it is possible to reduce the printing cost and improve the printing speed. Furthermore, dryness can also be improved.

(solvent)
The overcoat ink according to the present embodiment contains a solvent (dispersion medium) for dissolving (dispersing) the coating agent in addition to the coating agent described above. The overcoat ink according to the present embodiment may contain, as a solvent, at least one type of alcohol selected from water (for example, purified water), ethanol, isopropyl alcohol, and normal propyl alcohol. For example, as the solvent of the overcoat ink according to the present embodiment, any one of water (for example, purified water), ethanol, isopropyl alcohol, and normal propyl alcohol may be used alone, or two or more may be used in combination. may be used.

Moreover, the overcoat ink according to the present embodiment may contain water and any one of ethanol, isopropyl alcohol and normal propyl alcohol as a solvent. In this case, the content of water in the solvent is in the range of 3% by mass or more and 10% by mass or less with respect to the mass of the entire solvent, and at least one of ethanol, isopropyl alcohol and normal propyl alcohol in the solvent The content may be in the range of 90% by mass or more and 97% by mass or less with respect to the mass of the entire solvent. When the content of water and the content of the alcohol solvent in the solvent are within the ranges described above, the overcoat ink is imparted with a good balance between drying property and ejection stability. As a result, printed images formed with water-soluble ink can be more reliably protected, and the ejection stability of water-soluble ink can be more reliably improved.

Further, in the solvent in the overcoat ink according to the present embodiment, the ratio of the content of the alcohol solvent to the content of water is 1.2 or more and 19 or less (alcohol solvent: water = 1.2:1 or more and 19:1 or less). ) is preferably within the range of As a result, the overcoat ink is imparted with a better balance of drying property and ejection stability, and as a result, the printed image formed with the water-soluble ink is more reliably protected, and the water-soluble ink is used. Ejection stability can be improved more reliably.

The coating agent used in the overcoat ink tends to dissolve more easily in alcohol solvents than in water. Therefore, the solvent of the overcoat ink contains more alcohol solvent than water, so that the undissolved coating agent (precipitation) in the overcoat ink can be suppressed. Moreover, from the viewpoint of protecting the printed image, the overcoat ink is required to dry faster than the water-soluble ink. For this reason, the solvent in the overcoat ink according to the present embodiment preferably has a ratio of the content of the alcohol solvent to the content of water within the above range and contains a large amount of the alcohol solvent excellent in drying property. .
In addition, since the above-mentioned coating agent is compatible with water, the solvent for dissolving the coating agent should be a mixed solvent containing a small amount of water in addition to the alcohol solvent, compared to the case where the alcohol solvent is used alone. is preferred. Therefore, the solvent in the overcoat ink according to the present embodiment is a mixed solvent in which the ratio of the content of the alcohol solvent to the content of water is 9 or more and 19 or less (alcohol solvent:water = 9:1 or more and 19:1 or less). It is more preferable that As a result, it is possible to reliably provide the overcoat ink with a better balance between drying property and ejection stability, and to prevent solidification of the overcoat ink and precipitation of the coating agent in an inkjet head that ejects water-soluble ink. It can be suppressed more reliably.

In addition, ethanol, isopropyl alcohol, and normal propyl alcohol, which are alcohol solvents used in the overcoat ink, may cause white turbidity when used alone, so the solvent in the overcoat ink is preferably a mixed solvent with water. .

The overcoat ink according to this embodiment is preferably colorless and light-transmitting. Thereby, it is possible to suppress deterioration in visibility when the printed image is observed through the overcoat layer. However, the present invention is not limited to this, and the overcoat ink may be colored and have optical transparency as long as the visibility of the printed image is not adversely affected.

(Ultraviolet luminescent agent)
The overcoat ink according to the present embodiment may contain an ultraviolet light emitting agent (hereinafter also referred to as "UV light emitting agent") in addition to the coating agent and solvent described above.
As described above, the overcoat ink according to the present embodiment is preferably colorless and light transmissive. Therefore, it is difficult for a visible light camera having sensitivity in the visible light region to recognize an overcoat layer formed on a printing substrate (for example, a solid formulation).
By adding a UV luminescent agent to the overcoat ink, the overcoat layer can be recognized using UV illumination and a UV camera with a sensor sensitive to UV light. As a result, an inspection (UV inspection) is performed to confirm the formation state of the overcoat layer on the printing base material (for example, whether the overcoat layer is able to coat the printed image), and the solid formulation on which the printed image is formed A quality assessment can be performed on the printed part of (for example, a tablet).

The overcoat ink according to the present embodiment contains riboflavin having a solubility (at a temperature of 25° C.) of 0.05% or more in the solvent (at least one of water, ethanol, isopropyl alcohol, and normal propyl alcohol) as a UV light-emitting agent. It preferably contains a class.
This makes it possible to suppress the undissolved UV light-emitting agent during the production of the overcoat ink, and to ensure the solubility of the UV light-emitting agent in the solvent.

In addition, in the overcoat ink according to the present embodiment, the content of the UV light emitting agent (riboflavins in this example) is within the range of 0.001% by mass or more and 1.0% by mass or less of the total mass of the overcoat ink. Preferably.
When the content of the UV light-emitting agent is within the above range, the overcoat layer can be recognized by a UV camera during UV inspection, and the ejection stability of the overcoat ink can be improved.
Moreover, in the overcoat ink according to the present embodiment, the riboflavins used for the UV light emitting agent are preferably riboflavin butyrate, sodium riboflavin phosphate, or a mixture thereof.
The riboflavins described above emit strong light when irradiated with ultraviolet light, and even when added in a very small amount, the light emission can be confirmed with a UV camera. Moreover, by using the riboflavins described above, the overcoat ink can maintain its dryness and transparency.

Moreover, the overcoat ink according to the present embodiment may contain the same binder and leveling agent as those of the water-soluble ink described above, in addition to the coating agent, solvent, and UV emitting agent described above.

〔Printer〕
Next, a printing press according to this embodiment will be described with reference to FIG. FIG. 1 is a diagram schematically showing part of a printer 50 according to this embodiment.
The printer 50 according to this embodiment is a printer capable of printing with at least two types of inkjet inks. The two or more types of inkjet inks that can be printed by the printing machine 50 include an overcoat ink containing a coating agent that dissolves in both water and alcohol, and a water-soluble ink containing water as a main solvent and at least one coloring material. It is sufficient if at least ink is contained. In other words, the printer 50 can print using an ink set that includes at least the combination of the water-soluble ink and the overcoat ink described above.

Further, the printing machine 50 according to the present embodiment can print the overcoat ink according to the present embodiment overlaid on the printing substrate 15 after printing the water-soluble ink. As a result, the printing machine 50 according to the present embodiment can protect printed images using water-soluble ink, and can improve ejection stability of the water-soluble ink. Hereinafter, printing with water-soluble ink may be referred to as "pre-printing", and printing with overcoat ink after printing with water-soluble ink may be referred to as "post-printing".

As shown in FIG. 1, a printer 50 according to this embodiment includes an inkjet head 51 . The inkjet head 51 is configured to be able to eject the overcoat ink after ejecting the water-soluble ink. Specifically, the inkjet head 51 includes a pre-printing inkjet head (an example of a second inkjet head) 51a that ejects water-soluble ink, and a post-printing inkjet head (an example of the first inkjet head) 51b that ejects overcoat ink. Consists of

The printer 50 is configured such that the printing substrate 15 conveyed on the conveyor 52 passes under the pre-printing inkjet head 51a earlier than the post-printing inkjet head 51b. That is, the printing machine 50 according to the present embodiment is configured to eject the overcoat ink from the post-printing inkjet head 51b after the water-soluble ink is ejected from the pre-printing inkjet head 51a.
As a result, the printing machine 50 can pre-print the water-soluble ink on the printing substrate 15 and post-print the overcoat ink according to the present embodiment on the printed image formed by the pre-printing. . As described above, the printing press 50 according to the present embodiment is configured to be capable of executing an in-line process in which pre-printing processing and post-printing processing are performed within one printing press.

As shown in FIG. 1, in the printing press 50 according to the present embodiment, the time from the end of the post-printing pre-printing process by the inline process to the start of the post-printing process (post-printing start time) is 0.1 seconds or longer. It is preferably within a period of 0.0 seconds or less. At this time, the printing speed should be in the range of 200 mm/s to 2000 mm/s. As a result, the overcoat layer can be quickly formed on the printed image to protect the printed image while suppressing bleeding of the printed image formed with the water-soluble ink. In order to keep the post-printing start time within the above range, the pre-printing inkjet head 51a and the post-printing inkjet head 51b are provided at a close distance. For example, the distance between the centers of the inkjet heads 51a and 51b may be in the range of 40 mm to 200 mm.

As described above, in the printing machine 50 according to the present embodiment, since the pre-printing inkjet head 51a and the post-printing inkjet head 51b are close to each other, the post-printing inkjet head 51a and the post-printing inkjet head 51b are close to each other during post-printing printing, that is, during the formation of the overcoat layer. The overcoat ink ejected from the head 51b may scatter in the form of mist and adhere to the preprinting inkjet head 51a. Even in this case, the overcoat ink according to the present embodiment is soluble in water-soluble ink due to the structure including the coating agent that is soluble in both water and alcohol as described above. Therefore, coagulation of the overcoat ink adhering to the inkjet head 51a and deposition of the coating agent are suppressed, and the ejection stability of the water-soluble ink from the inkjet head 51a can be improved.

In addition, in the present invention, the configuration of the printer 50 is not limited to this. For example, the printer 50 may have one inkjet head. In this case, two systems of nozzles may be arranged in one inkjet, and the water-soluble ink for pre-printing may be ejected from one nozzle, and the overcoat ink for post-printing may be ejected from the other nozzle. . That is, the printing machine 50 ejects the water-soluble ink from one nozzle to perform pre-printing on the printing substrate 15, and then ejects the overcoat ink from another nozzle to the printing substrate 15. Post-printing may be performed.
Thus, the printer 50 may be equipped with one or more inkjet heads when the inkjet head has two systems of nozzles. Thus, two types of inkjet inks (water-soluble ink and overcoat ink in this example) can be ejected from one inkjet head, and printing can be performed using the two types of inkjet inks.

The printing machine 50 according to the present embodiment also includes a waste liquid mechanism 53 that is a mechanism for collecting the inkjet ink that has been ejected without a printing substrate due to nozzle maintenance of the inkjet head 51 or the like. The waste liquid mechanism 53 may be configured as a tray that stores the ejected inkjet ink, and discharges the ejected inkjet ink to a waste liquid reservoir provided at a predetermined position of the printing machine 50 or to the outside of the printing machine 50. You may be comprised as piping for. In addition, the receiving tray and piping used as the waste liquid mechanism 53 are divided into two systems, one for water-based ink and the other for overcoat ink, at the inlet into which the inkjet ink flows, and are integrated into one system inside. good too.

In the waste liquid mechanism 53, the ejected water-soluble ink and overcoat ink are mixed. Conventional overcoat inks that use water-insoluble coating agents can solidify in the waste system when mixed with water-soluble inks. It was necessary to provide a drainage mechanism for the ink. As a result, problems such as a complicated structure of the printing press, an increase in manufacturing cost, and an increase in the size of the printing press have arisen.
On the other hand, since the overcoat ink according to the present embodiment dissolves in the water-soluble ink as described above, solidification and deposition of the coating agent do not occur even when the overcoat ink is mixed with the water-soluble ink. For this reason, it is possible to integrate the waste liquid mechanism and use the common waste liquid mechanism 53 for the water-soluble ink and the overcoat ink. As a result, the printing press 50 according to the present embodiment can simplify the structure of the printing press, reduce the manufacturing cost, and further suppress an increase in the size of the printing press.

In addition, the printer 50 according to the present embodiment only needs to be capable of printing overcoat ink and water-soluble ink, which are inkjet inks, and can use an inkjet device such as an inkjet printer. Therefore, the overcoat ink and the water-soluble ink according to this embodiment have a wide range of applications and are very useful. Further, for example, the printing machine 50 according to the present embodiment may be a so-called drop-on-demand type ink jet device using a piezoelectric element (piezoelectric ceramics) as an actuator, or may be an ink jet device of another type.

Drop-on-demand ink-jet devices include, for example, devices employing a thermal ink-jet method in which ink is ejected using water vapor pressure generated by instantaneously heating minute heat-generating elements to a high temperature (200 to 300° C.), and actuators. An electrostatic type device that ejects ink jet ink by electrostatically vibrating a device, and a device that employs an ultrasonic system that utilizes the cavitation phenomenon of ultrasonic waves. In addition, if the inkjet ink (water-soluble ink and overcoat ink in this example) used in the printing machine 50 according to the present embodiment has charging performance, a device that employs a continuous injection method (continuous method) is used. It is also possible to use

〔tablet〕
In this embodiment, a tablet may be used as the substrate for printing. Specifically, the overcoat ink according to the present embodiment may be printed or printed on the surface of a tablet, for example, using the printer 50 . That is, the tablet according to the present embodiment only needs to have a printed portion printed using the overcoat ink according to the present embodiment, that is, a printed portion including at least an overcoat layer (for example, the overcoat layer 23). Further, if the overcoat layer is the overcoat ink according to the present embodiment, for example, it protects the printed image (for example, printed image 3) applied to the surface of the medical tablet using an inkjet printing method, and It is possible to suppress the solidification of the overcoat ink adhering to the inkjet head 51a and the deposition of the coating agent, thereby improving the ejection stability of the water-soluble ink. Hereinafter, the structure of a tablet provided with an overcoat layer printed with an overcoat ink according to the present embodiment and a printed image formed with a water-soluble ink will be described.
The tablet according to this embodiment is, for example, a medical tablet. Here, "medical tablets" include, for example, uncoated tablets (uncoated tablets), sugar-coated tablets, enteric-coated tablets, orally disintegrating tablets, as well as film-coated tablets in which a water-soluble surface layer is formed on the outermost surface of the tablet. This includes tablets and the like.

FIG. 2 is a schematic cross-sectional view showing an example of a printed medical tablet. In FIG. 2, in cross-sectional view, a printed image 3 such as characters is printed on the upper surface of the base material 1 of the tablet 100, which is an uncoated tablet, and an uncoated tablet printed material 5 provided with an overcoat layer 23 on the printed image 3 is shown. It is shown.
FIG. 3 is a schematic cross-sectional view showing an example of a printed (printed) medical tablet. In FIG. 3, in a cross-sectional view, a printed image 3 such as characters is printed on the upper surface of the base material 1 of the tablet 200, which is a film-coated tablet, and a film coat layer 7 is formed on the surface. A film-coated tablet print 9 with a print 30 provided with an overcoat layer 23 is shown.

As described above, the printed image 3 is formed with water-soluble ink, and the overcoat layer 23 is formed with the overcoat ink according to this embodiment. That is, the tablets 100 and 200 according to the present embodiment include the printed image 3 formed with a water-soluble ink containing water as a main solvent and containing at least one coloring material, and the overcoat ink overlaid on the printed image 3. a printing portion 30 having an overcoat layer 23 formed by printing with a
As a result, the tablets 100 and 200 according to the present embodiment can protect the printed image 3, suppress the solidification of the overcoat ink adhered to the inkjet head 51a and the deposition of the coating agent, and stabilize the discharge of the water-soluble ink. can improve sexuality.

4 is a plan view showing a configuration example of the tablet 100, and FIG. 5 is a plan view showing a configuration example of the tablet 200. As shown in FIG. As shown in FIGS. 4 and 5, in the tablets 100 and 200 according to this embodiment, the overcoat layer 23 is formed so as to cover the printed image 3 formed with water-soluble ink. As a result, the overcoat layer 23 can improve the dryness, abrasion resistance, etc. of the printed image 3 , prevent the printed image 3 from being transferred, and protect the printed image 3 .
In FIGS. 2 to 5, the overcoat layer 23 is illustrated by slanted shading for easy understanding, but as described above, the overcoat ink according to the present embodiment has optical transparency. Therefore, the overcoat layer 23 is not actually visible under visible light. Therefore, it is possible to suppress deterioration in visibility when the printed image 3 is observed through the overcoat layer 23 .
In the present invention, the print image 3 is not limited to characters, and a solid image may be printed. Also, for example, a two-dimensional barcode may be printed as the print image 3 on the tablet 200, which is a film-coated tablet.

The active ingredient contained in the medical tablet is not particularly limited. For example, substances effective in the prevention and treatment of various diseases (e.g., sleep-inducing action, tranquilizer activity, antibacterial activity, hypotensive action, anti-angina activity, analgesic action, anti-inflammatory activity, tranquilizing action, anti-diabetic activity, diuretic action) , anticholinergic activity, antihyperacid activity, antiepileptic activity, ACE inhibitory activity, β-receptor antagonist or agonist activity, narcotic activity, appetite suppressant activity, antiarrhythmic activity, antidepressant activity, anticoagulant activity, antidiarrheal activity , antihistamine activity, antimalarial activity, antitumor activity, immunosuppressive activity, antiparkinsonian activity, antipsychotic activity, antiplatelet activity, antihyperlipidemic activity, etc.), cleaning agent, perfume , substances having a deodorant action, etc., but are not limited to them.

The tablet according to the present embodiment may optionally contain an active ingredient and a carrier acceptable for its intended use. For example, in the case of medical tablets, a pharmaceutically acceptable carrier can be blended. As a pharmaceutically acceptable carrier, various organic or inorganic carrier substances commonly used as pharmaceutical materials are used, and for example, excipients, lubricants, binders, disintegrants, thickeners, etc. are appropriately blended in appropriate amounts. . Additives such as preservatives, antioxidants, coloring agents and sweeteners can also be used as necessary.

In the present embodiment, a medical tablet has been described as an example of a tablet, but the present invention is not limited to this. The printing target of the overcoat ink and the water-soluble ink according to the present embodiment is not particularly limited. You may print on the surface of various tablets, such as tablets and foods, such as a supplement. Moreover, the overcoat ink and the water-soluble ink according to the present embodiment are not particularly limited in the size of the object to be printed, and can be applied to tablets of various sizes.

(Tablet manufacturing method)
A method for producing tablets (for example, tablets 100 and 200) according to this embodiment includes at least a printing step of printing an overcoat ink according to this embodiment containing a coating agent that dissolves in both water and alcohol. Just do it. Further, the printing process includes a preprinting printing process of forming a print image 3 by printing a water-soluble ink containing water as a main solvent and containing at least one coloring material, and a print formed in the preprinting printing process. and a post-printing step of printing an overcoat ink over the image 3 .
According to the tablet manufacturing method according to the present embodiment, the formation of the overcoat layer 23 protects the printed image 3 printed on the tablet, and solidifies the overcoat ink adhered to the inkjet head 51a and precipitates the coating agent. can be suppressed to improve the ejection stability of the water-soluble ink.
Moreover, the printing process in the manufacturing method of the tablets 100 and 200 may be performed using the printer 50 according to the present embodiment described above.

(Effect of this embodiment)
(1) The overcoat ink, which is the inkjet ink according to the present embodiment, contains a coating agent that dissolves in both water and alcohol.
With such a configuration, the printed image can be protected, and the ejection stability of the water-soluble ink used as the preprinting ink can be improved as compared with the conventional technology.

(2) In addition, the coating agent contained in the overcoat ink, which is the inkjet ink according to the present embodiment, has a solubility in ethanol of 1% by mass, a solubility in isopropyl alcohol of 1%, and a solubility in normal propyl alcohol. 1%.
With such a configuration, even when the solvent in the overcoat ink according to the present embodiment is a mixed solvent composed of water and alcohol, the occurrence (precipitation) of undissolved coating agent is suppressed. , the ejection stability of the water-soluble ink used as the preprinting ink can be improved.

(3) Coating agents contained in the inkjet ink according to the present embodiment include methacrylic acid copolymer L, methacrylic acid copolymer LD, methacrylic acid copolymer S, aminoalkyl methacrylate copolymer E, ammonioalkyl methacrylate copolymer, hydroxypropyl cellulose, At least one of ethyl cellulose and polyvinyl acetal diethylaminoacetate should be included.
With such a configuration, the solubility conditions of the coating agent in each of water and alcohol solvents (ethanol, isopropyl alcohol, and normal propyl alcohol) are satisfied, and compared with the conventional technology, water-soluble ink, which is preprinting ink can improve the ejection stability.

(4) In addition, the content of the coating agent in the overcoat ink, which is the inkjet ink according to the present embodiment, is in the range of 1% by mass or more and 25% by mass or less with respect to the entire inkjet ink (overcoat ink). good too.
With such a configuration, both the protection of the printed image by improving the drying property of the printed image and the improvement in the ejection stability of the water-soluble ink, which is the overcoat ink and the preprinting ink, can be reliably achieved.
(5) Moreover, the overcoat ink, which is the inkjet ink according to the present embodiment, may contain at least one alcohol selected from water, ethanol, isopropyl alcohol, and normal propyl alcohol as a solvent.
With such a configuration, it is possible to improve the ejection stability of the water-soluble ink used as the preprinting ink and to improve the ejection stability of the overcoat ink, as compared with the conventional technology.
(6) In addition, the overcoat ink, which is the inkjet ink according to the present embodiment, contains water and an alcohol (at least one of ethanol, isopropyl alcohol, and normal propyl alcohol) as a solvent. The ratio of the content of alcohols to the content of may be in the range of 9 to 19 (alcohols: water = 9:1 to 19:1).
With such a configuration, the overcoat ink is imparted with a good balance of drying property and ejection stability, and solidification of the overcoat ink and deposition of the coating agent in the inkjet head that ejects the water-soluble ink are prevented. It can be suppressed more reliably.
(7) In addition, the overcoat ink, which is the inkjet ink according to the present embodiment, contains water and alcohol (at least one of ethanol, isopropyl alcohol, and normal propyl alcohol) as solvents, and the water content is is in the range of 3% by mass or more and 10% by mass or less with respect to the mass of the entire solvent, and the content of the alcohol is in the range of 90% by mass or more and 97% by mass or less with respect to the mass of the entire solvent There may be.
With such a configuration, it is possible to more reliably protect the printed image formed with the water-soluble ink, and to more reliably improve the ejection stability of the water-soluble ink, which is the preprinted ink.

(8) Moreover, the overcoat ink, which is the inkjet ink according to the present embodiment, may contain riboflavins having a solubility of 0.05% by mass or more in a solvent.
With such a configuration, it is possible to perform quality evaluation of the printed portion of the tablet according to the present embodiment by performing UV inspection.
(9) In addition, the riboflavins contained in the overcoat ink, which is the inkjet ink according to the present embodiment, is riboflavin butyrate, riboflavin sodium phosphate, or a mixture of the riboflavin butyrate and the riboflavin sodium phosphate. There may be.
With such a structure, light emission is strong when irradiated with ultraviolet light, and light emission can be confirmed with a UV camera even with a very small amount of addition. Moreover, by using the riboflavins described above, the overcoat ink can maintain its dryness and transparency.

(10) Moreover, the tablets 100 and 200 according to the present embodiment are provided with the printed portion 30 printed with the overcoat ink, which is the inkjet ink of (1) to (9) described above.
With such a configuration, it is possible to protect the printed image 3 in the printing unit 30 and improve the ejection stability of the water-soluble ink, which is the preprinted ink, compared to the conventional technology.
(11) In addition, the printed portion 30 in the tablets 100 and 200 according to the present embodiment is a printed image 3 formed with a water-soluble ink, which is an inkjet ink containing water as a main solvent and at least one coloring material, It may have an overcoat layer 23 formed by printing an overcoat ink, which is an inkjet ink, on the printed image 3 .
According to the tablet according to this embodiment, the overcoat layer 23 reliably protects the printed image 3 .

(12) Further, the printing machine 50 according to the present embodiment is a printing machine capable of printing at least two types of inkjet inks on the printing substrate 15, and the two or more types of inkjet inks include At least the overcoat ink, which is the inkjet ink of (1) to (9), and the water-soluble ink, which is the inkjet ink containing water as a main solvent and at least one coloring material, is included. Therefore, it is possible to print the overcoat ink after printing the water-soluble ink.
With such a configuration, the printed image can be protected, and the ejection stability of the water-soluble ink used as the preprinting ink can be improved as compared with the conventional technology.
(13) Further, the printing machine 50 according to the present embodiment includes the inkjet head 51 capable of ejecting the overcoat ink after ejecting the water-soluble ink.
With such a configuration, the printed image can be reliably protected, and the discharge stability of the water-soluble ink used as the preprinting ink can be further improved as compared with the conventional technology.
(14) Further, the printing machine 50 according to the present embodiment includes the post-printing inkjet head 51b that ejects the overcoat ink and the pre-printing inkjet head 51a that ejects the water-soluble ink. After ejecting the water-soluble ink, the overcoat ink may be ejected from the post-printing inkjet head 51b.
With such a configuration, the printed image 3 can be reliably protected, and the ejection stability of the water-soluble ink used as the preprinting ink can be more reliably improved as compared with the conventional technology. .

(15) In addition, the method for manufacturing tablets 100 and 200 according to the present embodiment includes at least a printing step of printing an overcoat that is inkjet ink containing a coating agent that dissolves in both water and alcohol.
With such a configuration, the printed image can be protected, and the ejection stability of the water-soluble ink used as the preprinting ink can be improved as compared with the conventional technology.
(16) In addition, the printing step in the method for manufacturing the tablets 100 and 200 according to the present embodiment includes forming the printed image 3 by printing a water-soluble ink containing water as a main solvent and containing at least one coloring material. It may include a pre-printing process and a post-printing process of printing overcoat ink on the printed image 3 formed in the pre-printing process.
With such a configuration, the printed image 3 can be reliably protected, and the ejection stability of the water-soluble ink used as the preprinting ink can be more reliably improved as compared with the conventional technology. .

[Example]
EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the Examples.
(Manufacture of water-soluble ink)
The procedure for preparing the water-soluble ink used as the preprinting ink in Examples and Comparative Examples will be described below.
As shown in Table 1 below, four types of water-soluble inks, ie, two types of dye inks (dye inks 1 and 2) and two types of pigment inks (pigment inks 1 and 2) were prepared. Each water-soluble ink contains each component of a coloring material, an organic solvent, water, and an additive (dispersant, binder). As for the order of preparation, first, water and an organic solvent were mixed to obtain a mixed solvent. Next, a coloring material was added to the mixed solvent, and then additives were added as necessary. Finally, this mixed liquid was placed in a dispersing machine such as a paint shaker, and finely divided and dispersed for a specified period of time. Thus, a water-soluble inkjet ink was prepared as a preprinting ink according to this example. Various components will be specifically described below.

Purified water (ion-exchanged water) was used as the water constituting the water-soluble ink.
As the coloring material, Blue No. 1 was used for the dye ink, and bamboo charcoal (carbon) was used for the pigment ink.
Ethanol, propylene glycol, and glycerin were used as organic solvents, respectively.
As additives, sucrose fatty acid ester (Daiichi Kogyo Seiyaku Co., Ltd., DK Ester SS) was used as a dispersant, and reduced isomaltulose was used as a binder.
Solid foreign matter in the liquid was removed by passing each of the above water-soluble inks through a membrane filter. Specifically, the purified ink was obtained by passing through a membrane filter (cellulose acetate membrane) with a diameter of 5.0 μm once and then through a membrane filter (cellulose acetate membrane) with a diameter of 0.8 μm once.
Table 1 shows the composition of each water-soluble ink (dye inks 1 and 2 and pigment inks 1 and 2). "-" in Table 1 indicates that the substance was not used.

The procedures for preparing the overcoat inks in Examples and Comparative Examples are described below.
(Manufacture of overcoat ink)
The overcoat ink contains components of a coating agent, a drying solvent, water, and a UV light emitting agent. As for the order of preparation, the solvent was obtained first. As solvents, water and dry solvents (ethanol, isopropyl alcohol (IPA), normal propyl alcohol (NPA)) were used alone or in combination. Next, a coating agent was added to the solvent, and a UV light emitting agent was added as necessary. Finally, this mixed liquid was placed in a dispersing machine such as a paint shaker, and finely divided and dispersed for a specified period of time. Thus, an overcoat ink, which is an inkjet ink according to this example, was prepared.

Solid foreign matter in the liquid was removed by passing each of the above-mentioned overcoat inks through a membrane filter. Specifically, the purified ink was obtained by passing through a membrane filter (cellulose acetate membrane) with a diameter of 5.0 μm once and then through a membrane filter (cellulose acetate membrane) with a diameter of 0.8 μm once.
The compositions of Examples 1 to 143 and Comparative Examples 1 and 2 are shown in Tables 2 to 8 below. In Tables 2 to 8, "-" in the column "Overcoat ink composition" indicates that the substance was not used.

<Evaluation>
With respect to the above purified inks using the overcoat inks of the above Examples and Comparative Examples, ejection stability, printed image transfer resistance evaluation, and UV emission performance were evaluated by the following methods. The evaluation results are shown in Tables 2 to 8 together with the ink compositions of the above Examples and Comparative Examples. "-" in the "Evaluation" column in Tables 2 to 8 indicates that the ink was not used or the evaluation was not performed.

<Discharge stability evaluation>
As shown in Tables 2 to 8, in the evaluation, dyes 1 and 2 and pigments 1 and 2 were used as preprinted inks as water-soluble inks. For example, in Examples 9 to 52, pre-printing with each of the four types of water-soluble inks, dyes 1 and 2 and pigments 1 and 2, and post-printing with an overcoat ink were performed at each evaluation. That is, each of the four water-soluble inks was combined with the overcoat ink for printing.
(1) Continuous printability evaluation As an inkjet head for pre-printing, the print resolution is 600 dpi in the main scanning direction, 600 dpi in the sub-scanning direction (conveyance direction of recording media such as tablets), and the total number of nozzles is 2,656. An on-demand type inkjet head was used. Further, the ink jet for post-printing and the head have the same configuration. Then, after flushing for a specified time (5 to 30 minutes), a test pattern is continuously printed using an inkjet head with a printing drop amount of 6 pl per drop, and whether or not it is possible to eject from all nozzles without an ejection failure amount. It was confirmed. At this time, the distance between the centers of the two inkjet heads was set to 100 mm. The printing speed was set to 300 mm/s, and the time from the end of the preprinting process to the start of the postprinting process was set to 0.5 seconds.
In addition, in Tables 2 to 8, the continuous printing time during which ink could be ejected was measured as the evaluation results of continuous printing properties. Evaluation criteria are as follows.
◎: Continuous printing time of 30 minutes or more ○+: Continuous printing time of 20 minutes or more and less than 30 minutes ○: Continuous printing time of 10 minutes or more and less than 20 minutes △: Continuous printing time of 5 minutes or more and less than 10 minutes ×: Continuous printing less than 5 minutes

(2) Evaluation of intermittent resumability The ink jet head for pre-printing has a print resolution of 600 dpi in the main scanning direction, 600 dpi in the sub-scanning direction (conveyance direction of recording media such as tablets), and a piezoelectric ceramic drive with a total of 2,656 nozzles. A drop-on-demand type inkjet head was used. Further, the ink jet for post-printing and the head have the same configuration. After leaving the ink in the inkjet head for a specified time (5 to 30 minutes) without flushing, the inkjet head was used to print a test pattern with a print drop amount of 6 pl per drop. Then, it was confirmed from the printing state of the test pattern whether or not the ink could be ejected from all the nozzles without any non-ejection amount. At this time, the distance between the centers of the two inkjet heads was set to 100 mm. The printing speed was set to 300 mm/s, and the time from the end of the preprinting process to the start of the postprinting process was set to 0.5 seconds.
In Tables 2 to 8, as the evaluation results of the intermittent resumability, the standing time during which the ink can be ejected was measured. Evaluation criteria are as follows.
◎: 30 minutes or longer for ink ejection ○+: 20 to 30 minutes for ink ejection 〇: 10 to 20 minutes for ink ejection △ : 5 minutes or more and less than 10 minutes left for ink ejection x : Less than 5 minutes left for ink ejection

<Print image transfer resistance evaluation>
(1) Evaluation of dryness by transfer test For the following two types of tablets 1 and 2, the print resolution is 600 dpi in the main scanning direction, the sub-scanning direction (conveyance direction of recording media such as tablets) 600 dpi, and the total number of nozzles is 2,656. Using a piezoelectric ceramic-driven drop-on-demand inkjet head, images were printed (pre-printed) with a water-soluble ink (dye ink 1 in Table 1) at a printing drop amount of 10 pl per drop. Furthermore, using the same drop-on-demand inkjet head as that used for printing the water-soluble ink, the overcoat ink according to each example and each comparative example was printed on each of the tablets 1 and 2 (post-printing). )did. At this time, the distance between the centers of the two inkjet heads was set to 100 mm. The printing speed was set to 300 mm/s, and the time from the end of the preprinting process to the start of the postprinting process was set to 0.5 seconds.
As samples for comparison, tablets 1 and 2 printed with only water-soluble ink (dye ink 1) were separately prepared.
・Tablet 1 (film-coated tablet)
Tablet type Tablet 2 (difficult-to-print tablet) in which a coating layer is formed on the surface of a tablet by incorporating polyethylene glycol, titanium oxide pigment, etc. into hydroxypropylcellulose, hydroxypropylmethylcellulose, etc.
A tablet type in which a coating layer is formed on the surface of the tablet by adding polyethylene glycol, titanium oxide pigment, etc. to polyvinyl alcohol.

10 seconds after printing, the water-soluble ink (dye ink 1) and the overcoat ink according to each example and each comparative example were printed on the tablet, and the tablet was attached to a digital force gauge. Contact was made for 4 to 0.5 seconds to confirm whether or not the printed ink was transferred. Similarly, a tablet attached to a digital force gauge is brought into contact with a tablet printed with only water-soluble ink at a pressure of 2 to 3 N for 0.4 to 0.5 seconds, and whether or not the printed ink is transferred. It was confirmed.
In addition, in Tables 2 to 8, the density of the transferred ink was visually observed as a result of evaluation of drying property. Evaluation criteria are as follows.
◎ : No transfer of water-soluble ink ○＋ : Transfer of water-soluble ink is very slight and difficult to visually confirm 〇 : Transferred water-soluble ink is light in color but can be visually confirmed △ : When the transferred water-soluble ink is lighter than the water-soluble ink alone, but the transferred water-soluble ink is darker. × : When the water-soluble ink is transferred darker than the water-soluble ink alone.

<UV light emission performance evaluation>
The overcoat inks of Examples 39 to 52, Examples 83 to 96, and Examples 127 to 140 to which a UV light emitting agent was added were evaluated for UV light emission performance as follows.
(1) Solubility evaluation During the production of the overcoat ink according to each of the above-described examples to which the UV light emitting agent was added, it was visually observed whether or not the UV light emitting agent remained undissolved in the solvent after dispersion processing using a dispersing machine. decided by Evaluation criteria are as follows.
〇: No undissolved residue was visually confirmed ×: Undissolved residue was visually confirmed

(2) Emission amount evaluation The overcoat ink according to each of the above-described examples to which a UV light emitting agent was added was diluted 33 times, and a fluorescence photometer "RF5300-PC manufactured by Shimadzu Corporation" was used under the following conditions. Fluorescence photometry was performed to confirm the numerical value of the amount of light emitted when irradiated with ultraviolet rays.
The excitation wavelength was set at 445 nm, and fluorescence wavelengths from 400 nm to 700 nm were measured.
The scanning speed was set to Fast, and the sampling interval was set to 1.0 nm.
The band width was set to 1.5 nm for both excitation and fluorescence, the sensitivity was set to High, and the response was set to Auto to measure the amount of luminescence.
Evaluation criteria are as follows.
◎: luminescence level 50 or more ○: luminescence level 20 or more and less than 50 △: luminescence level 10 or more and less than 20 ×: luminescence level less than 10 In addition, even if the result of UV luminescence performance evaluation is unsatisfactory, the quality of the tablet will not be considered. No problem.

Tables 2 to 8 show the composition and evaluation results of the overcoat inks of each example and comparative example.

(Evaluation result of ejection stability)
As shown in Tables 2 to 8, the overcoat inks and water-soluble inks of Examples 1 to 143 were evaluated for ejection stability (continuous printability evaluation, intermittent printability evaluation) and printed image transfer resistance (drying property). All the evaluation results were "△" or higher (accepted).
Specifically, in Examples 1 to 143, the continuous printability evaluation and the intermittent printability evaluation of the preprinting ink (water-soluble ink) were all passed, so preprinting with water-soluble ink and overcoat ink When post-printing is performed with water-soluble ink, the occurrence of coagulation of overcoat ink and deposition of coating agent attached to the inkjet head of water-soluble ink is suppressed, and the ejection stability of water-soluble ink is improved. Do you get it. In other words, it was found that the overcoat inks of Examples 1 to 143 can improve the ejection stability of water-soluble inks. Similarly, the post-printing inks (overcoat inks) of Examples 1 to 143 all passed the continuous printability evaluation and the intermittent printability evaluation, and the overcoat inks themselves of Examples 1 to 140 had stable ejection properties. It was found that performance was improved.
Furthermore, since all the results of the printed image transfer resistance evaluation (drying property) are acceptable, the overcoat inks of Examples 1 to 143 have excellent drying properties, and can be used to print images formed with water-soluble inks. I know it can be protected.
In other words, it was found that the overcoat inks of Examples 1 to 143 were able to protect the printed image and improve the ejection stability of the water-soluble preprinting ink.

On the other hand, as shown in Table 8, the overcoat inks and water-soluble inks of Comparative Examples 1 and 2 were evaluated for ejection stability (continuous printability evaluation, intermittent printability evaluation) or printed image transfer resistance evaluation results. included “×” (failed).
Specifically, the overcoat ink and the water-soluble ink of Comparative Example 1 were rated "x" in both the ejection stability evaluation and the printed image transfer resistance (drying property) evaluation. The ejection stability was insufficient and the printed image was not sufficiently protected. In addition, the overcoat ink and the water-soluble ink of Comparative Example 2 were evaluated as "Poor" in the evaluation of the printed image transfer resistance, and the drying property was insufficient. was not protected.

From the results of the above ejection stability evaluation and printed image transfer resistance evaluation, it was found that an overcoat ink containing a coating agent that is soluble in both water and alcohol protects the printed image and maintains the ejection stability of the water-soluble ink. was found to be sufficiently improved.

(Evaluation results of UV emission performance)
Further, as shown in Tables 4, 6, and 8, from the results of the UV emission performance evaluation in Examples 39 to 50, Examples 83 to 94, and Examples 127 to 138, water, ethanol, All overcoat inks containing riboflavins (riboflavin butyrate or riboflavin sodium phosphate) having a solubility of 0.001% or more in at least one of isopropyl alcohol and normal propyl alcohol have a solubility of “△” ( passed). In particular, Examples 41 to 44, Examples 47 to 50, Examples 85 to 88, Examples 91 to 94, and Examples 41 to 44, Examples 47 to 50, Examples 85 to 88, and Examples 91 to 94, in which the amount of the riboflavin added is 0.01% by mass or more relative to the mass of the entire overcoat ink. The overcoat inks of Examples 129 to 132 and Examples 135 to 138 had a light emission amount of 50 or more (⊚), indicating particularly high UV light emission performance.
In contrast, in the overcoat inks of Examples 51, 52, 95, 96, 139, and 140 containing the UV light-emitting agent (riboflavin) that does not satisfy the solubility conditions described above, both the solubility and the amount of light emitted were evaluated as It was found to be "x", and the UV emission performance was lower than that of the overcoat inks according to the above-described examples containing 0.001% or more of riboflavins satisfying the above-described solubility.

The scope of the invention is not limited to the illustrated and described exemplary embodiments, but also includes all embodiments that provide equivalent results for which the invention is intended. Furthermore, the scope of the invention is not limited to the combination of inventive features defined by the claims, but may be defined by any desired combination of the particular features of all individual disclosed features.

1 Base material 3 Printed image 5 Uncoated tablet printed material 7 Film coat layer 9 Film coated tablet printed material 15 Base material for printing 23 Overcoat layer 30 Printing part 50 Printers 51, 51a, 51b Inkjet head 52 Conveyor 53 Waste liquid mechanism 100, 200 Tablet

In order to achieve the above object, an inkjet ink according to one aspect of the present invention is an overcoat ink containing a coating agent that dissolves in both water and alcohol ,
The coating agent has a solubility of 0.5% by mass or more in a solvent having a mass ratio of alcohols to water at 25° C. (alcohols:water) of 1:1,
The content of the coating agent is in the range of 0.85% by mass or more and 2.5% by mass or less with respect to the entire inkjet ink .
In order to achieve the above objects, an inkjet ink according to another aspect of the present invention is an overcoat ink containing a coating agent that dissolves in both water and alcohol, wherein the coating agent has a temperature of 25°C. ammonioalkyl methacrylate copolymer having a solubility of 0.5% by mass or more in a solvent in which the mass ratio of alcohols to water (alcohols:water) is 1:1, and the content of the coating agent is 5% by mass of the entire ink, and contains water and ethanol as solvents, and the solvent has a ratio of ethanol content to water content of 19 (ethanol:water = 19:1) characterized by

In order to achieve the above object, a method for producing a tablet according to one aspect of the present invention includes a printing step of printing a first inkjet ink, which is an overcoat ink containing a coating agent that dissolves in both water and alcohol. and the first inkjet ink has a solubility of 0.5% by mass in a solvent in which the mass ratio of alcohols to water at 25° C. (alcohols:water) is 1:1 as the coating agent The above coating agent is included, and the content of the coating agent is in the range of 0.85% by mass or more and 2.5% by mass or less with respect to the entire inkjet ink .

To achieve the above object, an inkjet ink according to one aspect of the present invention is an overcoat ink containing a coating agent that dissolves in both water and alcohols, and the alcohols include ethanol, isopropyl alcohol and normal alcohol. It is at least one kind of propyl alcohol, and the coating agent has a solubility of 0.5% by mass or more in a solvent in which the mass ratio of the alcohol to water at 25° C. ( the alcohol:water) is 1:1. comprising at least one of methacrylic acid copolymer L, methacrylic acid copolymer LD, methacrylic acid copolymer S, aminoalkyl methacrylate copolymer E, ammonioalkyl methacrylate copolymer, hydroxypropyl cellulose, ethyl cellulose and polyvinyl acetal diethylaminoacetate ; The content of the coating agent is in the range of 0.85% by mass or more and 2.5% by mass or less with respect to the entire inkjet ink.
In order to achieve the above object, an inkjet ink according to another aspect of the present invention is an overcoat ink containing a coating agent that dissolves in both water and alcohols, and the alcohols are ethanol. , isopropyl alcohol and normal propyl alcohol, the coating agent is an ammonioalkyl methacrylate copolymer, and the mass ratio of the alcohol to water at 25 ° C. ( the alcohol: water) is 1 : 1, the content of the coating agent is 5% by mass with respect to the entire inkjet ink, the solvent contains water and ethanol, and the solvent is characterized by a ratio of ethanol content to water content of 19 (ethanol:water=19:1).

In order to achieve the above object, a method for producing a tablet according to one aspect of the present invention includes printing a first inkjet ink, which is an overcoat ink containing a coating agent that dissolves in both water and alcohols . wherein the alcohol is at least one of ethanol, isopropyl alcohol, and normal propyl alcohol, and the first inkjet ink contains, as the coating agent, a mass ratio of the alcohol and water The solubility in a solvent in which ( the alcohol:water) is 1:1 is 0.5% by mass or more, and methacrylic acid copolymer L, methacrylic acid copolymer LD, methacrylic acid copolymer S, aminoalkyl methacrylate copolymer E, A coating agent containing at least one of ammonioalkyl methacrylate copolymer, hydroxypropyl cellulose, ethyl cellulose, and polyvinyl acetal diethylaminoacetate is included, and the content of the coating agent is 0.85% by mass or more relative to the entire inkjet ink. It is characterized by being within the range of 2.5% by mass or less.

Claims (16)

An inkjet ink characterized by being an overcoat ink containing a coating agent soluble in both water and alcohol. 2. The coating agent according to claim 1, wherein the solubility in ethanol is 1% by mass or more, the solubility in isopropyl alcohol is 1% by mass or more, and the solubility in normal propyl alcohol is 1% by mass or more. Inkjet ink as described. The coating agent contains at least one of methacrylic acid copolymer L, methacrylic acid copolymer LD, methacrylic acid copolymer S, aminoalkyl methacrylate copolymer E, ammonioalkyl methacrylate copolymer, hydroxypropyl cellulose, ethyl cellulose and polyvinyl acetal diethylaminoacetate. The inkjet ink according to claim 1 or 2, characterized by: The inkjet ink according to any one of Claims 1 to 3, wherein the content of the coating agent is in the range of 1% by mass or more and 25% by mass or less with respect to the entire inkjet ink. 5. The inkjet ink according to any one of claims 1 to 4, wherein the solvent contains at least one alcohol selected from water, ethanol, isopropyl alcohol and normal propyl alcohol. The solvent includes water and the alcohol,
The solvent has a ratio of the content of the alcohol to the content of water in the range of 9 or more and 19 or less (the alcohol: water = 9:1 or more and 19:1 or less). 5. The inkjet ink according to 5. The solvent includes water and the alcohol,
The content of water is in the range of 3% by mass or more and 10% by mass or less with respect to the mass of the entire solvent,
6. The inkjet ink according to claim 5, wherein the content of the alcohol is in the range of 90% by mass or more and 97% by mass or less with respect to the total mass of the solvent. 8. The inkjet ink according to any one of claims 5 to 7, comprising riboflavins having a solubility in the solvent of 0.05% by mass or more. The inkjet ink according to claim 8, wherein the riboflavins are riboflavin butyrate, riboflavin sodium phosphate, or a mixture of the riboflavin butyrate and the riboflavin sodium phosphate. A tablet comprising a printed portion printed using the first inkjet ink, which is the inkjet ink according to any one of claims 1 to 9. The printing unit
a printed image formed with a second inkjet ink containing water as a main solvent and at least one colorant;
11. The tablet according to claim 10, further comprising an overcoat layer formed by overlaying and printing the first inkjet ink on the printed image. A printing machine capable of printing at least two types of inkjet inks on a printing substrate,
The two or more types of inkjet inks include the first inkjet ink, which is the inkjet ink according to any one of claims 1 to 9, and the second inkjet ink, which contains water as a main solvent and at least one coloring material. contains at least two inkjet inks,
A printing machine, wherein the first inkjet ink can be overlapped and printed after printing the second inkjet ink on the substrate for printing. 13. The printing machine according to claim 12, further comprising an inkjet head capable of ejecting the first inkjet ink after ejecting the second inkjet ink. a first inkjet head that ejects the first inkjet ink;
a second inkjet head that ejects the second inkjet ink,
13. The printing machine according to claim 12, wherein the first inkjet ink is ejected from the first inkjet head after the second inkjet head ejects the second inkjet ink. A method for producing a tablet, comprising at least a printing step of printing a first inkjet ink, which is an overcoat ink containing a coating agent soluble in both water and alcohol. The printing step includes
a pre-printing step of printing a second inkjet ink containing water as a main solvent and containing at least one coloring material to form a predetermined print image;
16. The method for producing a tablet according to claim 15, further comprising a post-printing step of printing the first inkjet ink over the printed image formed in the pre-printing step.

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